1. Field of the Invention
The present invention relates to a system to reduce complexity of Fast Fourier Transform (FFT) calculation used in a transmitting/receiving end of a Non-Continuous Orthogonal Frequency Division Multiplexing (NC-OFDM) that may be used in a cognitive radio environment, and an algorithm that may be applied to the system.
2. Description of Related Art
A Non-Continuous Orthogonal Frequency Division Multiplexing (NC-OFDM) may avoid a frequency band, currently used by licensed users, and may transmit/receive data using only frequency bands not being otherwise used, by using a spectrum sensing method.
That is, the OFDM may not use a subcarrier corresponding to a frequency band, used by licensed users, by disable use of the subcarrier, and may use remaining frequency bands by activating the remaining frequency band.
A transmitting/receiving end using the OFDM may efficiently perform modulation and demodulation using a Fast Fourier Transform (FFT) algorithm. However, since an OFDM may disable a plurality of subcarriers, all hardware resources of FFT may not be used.
Accordingly, when a subcarrier is disabled, a new approach to efficiently perform a FFT may be required to perform OFDM.